After the president told members of Congress that the plan would not pay for treating illegal immigrants, boos and hisses could be heard to Obama's left. Wilson's voice rose above the clatter, shouting, "You lie!"

Speaking near his Capitol Hill office on Thursday, Wilson called his outburst "spontaneous" and said he had apologized in a call to the White House.

"I taught Joe Wilson's kids. He is a good guy. I don't think this is in keeping with him," said Dave Woodard, a Clemson University political science professor who has known Wilson for years.

"He's a decent guy," Woodard added. "We all make mistakes, and I think he made a mistake."

Addison Graves "Joe" Wilson represents South Carolina's 2nd Congressional District, a California-shaped swath with population concentrated in Lexington County in the middle of the state but which stretches to Beaufort and Hilton Head Island in the southeast corner. The district has been represented by Republicans since 1965, according to OpenCongress.org. Watch Wilson's outburst and the reaction »

Thirty-year congressman Floyd Spence designated Wilson, a former state senator, as his heir apparent. The former aide to the late conservative Sen. Strom Thurmond and lawyer in the Reagan administration succeeded Spence in 2001, and voters have retained him since.

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"For eight years during the Bush administration, he was a pretty reliable supporter of the president and his policies, and he toes the Republican line pretty much right according to their platform," said John O'Connor, who covers politics for The State newspaper in the capital, Columbia.

Wilson was re-elected in 2008 with about 54 percent of the vote, matching Sen. John McCain's percentage in the presidential race in the 2nd District, according to Congressional Quarterly.

Wilson is a "far-right Republican," according to an analysis of bill sponsorships by the independent Web site Govtrack.us, which also calls him a leader based on other members' support for legislation he sponsors.

Wilson has sponsored 119 bills and seen one become law, according to Govtrack. He serves on three committees: Armed Services, Education and Labor, and Foreign Affairs.

"I think he feels the way a lot of people in South Carolina feel about [health reform]," O'Connor said. "They're suspicious. They're worried. There's some fear out there about what could happen."

In the hours after Wilson's catcall, $200,000 in campaign contributions poured in for Rob Miller, his Democratic opponent in the last and next election, according to the Democratic Congressional Campaign Committee. Watch viewers react to Obama's speech »

"Representative Wilson's behavior tonight exemplifies everything that is wrong in Washington," Miller said in a statement. "Instead of engaging in childish name-calling and disrespecting our commander-in-chief, Joe Wilson should be working towards a bipartisan solution that makes quality, affordable health care available to each and every South Carolinian."

Nevertheless, Wilson has little to worry about in South Carolina, Woodard said.

"That's going to be a real hard seat [for Miller] to win, even if he has" raised a lot of money, Woodard said. "They may get rid of Joe, but it won't be over this."

Miller reported $96,000 in contributions, including about $24,000 from himself, in his most recent Federal Election Commission filing. Five individuals, including three named Miller, had donated $2,400 each.

Wilson reported raising $284,000 in the current election cycle. His top individual contributor is the American Hospital Association's political action committee, which gave him $7,000, according to the Center for Responsive Politics. The "health professionals" industry has contributed $19,000, the center reported.

All four of Wilson's sons are Eagle Scouts and military veterans. The eldest, Alan, is running for South Carolina attorney general in 2010 and has a good chance to win, Woodard said.

The Clemson professor said he's troubled by the lack of decorum Wilson's outburst typifies.

"This town meeting atmosphere of extremism and lack of respect bothers me," he said. "Seems like we're living in uncivil times. The emotion of this issue has been pretty intense this summer, and this is an extension of that."